Since the early 1980s, thousands of patients prone to irregular and sometimes life-threatening heart rhythms have had miniature heart monitors, particularly defibrillators and cardioverters, implanted in their bodies. These devices detect onset of abnormal heart rhythms and automatically apply corrective electrical therapy, specifically one or more bursts of electric current, to hearts. When the bursts of electric current are properly sized and timed, they restore normal heart function without human intervention, sparing patients considerable discomfort and often saving their lives.
The typical defibrillator or cardioverter includes a set of electrical leads, which extend from a sealed housing into the walls of a heart after implantation. Within the housing are a battery for supplying power, monitoring circuitry for detecting abnormal heart rhythms, and a capacitor for delivering bursts of electric current through the leads to the heart.
The capacitor may take the form of a flat aluminum electrolytic capacitor. This type of capacitor generally includes a stack of flat capacitive elements, with each capacitive element including a paper separator between two sheets of aluminum foil. The aluminum foil layers are divided into a group of anode layers and a group of cathode layers.
The anodes and the cathodes of the capacitor elements are connected together to provide a total capacitance. After being connected, the respective anodes and cathodes are connected to terminals for being coupled to circuitry outside the capacitor case. These internal and external connections can be time-consuming to make and can take up valuable space both within and outside the capacitor.
Since defibrillators and cardioverters are typically implanted in the left region of the chest or in the abdomen, a smaller size device, which is still capable of delivering the required level of electrical energy, is desirable.
Accordingly, there is a need for capacitor structures and methods of manufacture which provide greater process control, less expensive manufacturing, provide for a design efficiently utilizing space within the capacitor case, and provide for a compact capacitor design capable of providing the required pulse of energy for use within the implantable device.